Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities from continuing operations	$ (27.0)	$ (12.4)	$ (29.7)
Investing activities:
Investment in affiliated companies	0.0	0.0	0.0
Cash paid for acquisitions, net of cash acquired	0.0	(5.1)	0.0
Change in restricted cash	0.0	0.3	4.7
Capital expenditures	(26.5)	(9.2)	(11.3)
Proceeds from sale of assets	0.7	0.1	0.9
Net cash used in investing activities from continuing operations	(25.8)	(13.9)	(5.7)
Financing activities:
Proceeds from the issuance of long-term debt	300.0	0.0	0.0
Extinguishment of long-term debt	(448.8)	(14.1)	(175.0)
Repayments under credit facility	(1.0)	(1.0)	(42.0)
Debt issuance costs	(6.6)	0.0	0.0
Proceeds from the issuance of common stock	269.1	76.2
Proceeds from exercise of restricted stock units, employee stock options, and employee stock purchase plan	0.7	2.0	3.4
Financing from affiliated companies	0.0	0.0	0.0
Other, net			(1.1)
Net cash provided by (used in) financing activities from continuing operations	113.4	63.1	(214.7)
Net cash flows of continuing operations	60.6	36.8	(250.1)
Net operating cash flows of discontinued operations	0.0	0.1	2.8
Net investing cash flows from discontinued operations	(0.6)	4.0	242.5
Effect of exchange rate changes on cash and cash equivalents	0.5	(0.3)	(0.2)
Net increase (decrease) in cash and cash equivalents	60.5	40.6	(5.0)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities from continuing operations	0.0	0.0	0.0
Investing activities:
Investment in affiliated companies	33.2	3.0	33.8
Cash paid for acquisitions, net of cash acquired		0.0
Change in restricted cash		0.0	0.0
Capital expenditures	0.0	0.0	0.0
Proceeds from sale of assets	0.0	0.0	0.0
Net cash used in investing activities from continuing operations	33.2	3.0	33.8
Financing activities:
Proceeds from the issuance of long-term debt	0.0
Extinguishment of long-term debt	0.0	0.0	0.0
Repayments under credit facility	0.0	0.0	0.0
Debt issuance costs	0.0
Proceeds from the issuance of common stock	0.0	0.0
Proceeds from exercise of restricted stock units, employee stock options, and employee stock purchase plan	0.0	0.0	0.0
Financing from affiliated companies	(33.2)	(3.0)	(33.8)
Other, net			0.0
Net cash provided by (used in) financing activities from continuing operations	(33.2)	(3.0)	(33.8)
Net cash flows of continuing operations	0.0	0.0	0.0
Net operating cash flows of discontinued operations		0.0	0.0
Net investing cash flows from discontinued operations	0.0	0.0	0.0
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0	0.0
Net increase (decrease) in cash and cash equivalents	0.0	0.0	0.0
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities from continuing operations	(25.9)	(26.3)	(2.0)
Investing activities:
Investment in affiliated companies	(33.2)	0.0	(33.8)
Cash paid for acquisitions, net of cash acquired		0.0
Change in restricted cash		0.0	0.0
Capital expenditures	(0.8)	(0.5)	(1.0)
Proceeds from sale of assets	0.0	0.0	0.0
Net cash used in investing activities from continuing operations	(34.0)	(0.5)	(34.8)
Financing activities:
Proceeds from the issuance of long-term debt	300.0
Extinguishment of long-term debt	(448.8)	(14.1)	(175.0)
Repayments under credit facility	0.0	0.0	(41.0)
Debt issuance costs	(6.6)
Proceeds from the issuance of common stock	269.1	76.2
Proceeds from exercise of restricted stock units, employee stock options, and employee stock purchase plan	0.7	2.0	3.4
Financing from affiliated companies	0.0	3.0	0.0
Other, net			0.0
Net cash provided by (used in) financing activities from continuing operations	114.4	67.1	(212.6)
Net cash flows of continuing operations	54.5	40.3	(249.4)
Net operating cash flows of discontinued operations		0.4	0.0
Net investing cash flows from discontinued operations	(0.6)	4.0	243.2
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0	0.0
Net increase (decrease) in cash and cash equivalents	53.9	44.7	(6.2)
Subsidiary Guarantors on a Combined Basis
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities from continuing operations	(8.8)	16.6	(30.8)
Investing activities:
Investment in affiliated companies	0.0	(3.0)	0.0
Cash paid for acquisitions, net of cash acquired		(5.1)
Change in restricted cash		0.3	4.7
Capital expenditures	(23.9)	(7.1)	(9.5)
Proceeds from sale of assets	0.7	0.1	0.9
Net cash used in investing activities from continuing operations	(23.2)	(14.8)	(3.9)
Financing activities:
Proceeds from the issuance of long-term debt	0.0
Extinguishment of long-term debt	0.0	0.0	0.0
Repayments under credit facility	0.0	0.0	0.0
Debt issuance costs	0.0
Proceeds from the issuance of common stock	0.0	0.0
Proceeds from exercise of restricted stock units, employee stock options, and employee stock purchase plan	0.0	0.0	0.0
Financing from affiliated companies	33.2	0.0	33.8
Other, net			(1.1)
Net cash provided by (used in) financing activities from continuing operations	33.2	0.0	32.7
Net cash flows of continuing operations	1.2	1.8	(2.0)
Net operating cash flows of discontinued operations		(0.3)	3.1
Net investing cash flows from discontinued operations	0.0	0.0	(0.4)
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0	0.0
Net increase (decrease) in cash and cash equivalents	1.2	1.5	0.7
Non-Guarantors on a Combined Basis
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities from continuing operations	7.7	(2.7)	3.1
Investing activities:
Investment in affiliated companies	0.0	0.0	0.0
Cash paid for acquisitions, net of cash acquired		0.0
Change in restricted cash		0.0	0.0
Capital expenditures	(1.8)	(1.6)	(0.8)
Proceeds from sale of assets	0.0	0.0	0.0
Net cash used in investing activities from continuing operations	(1.8)	(1.6)	(0.8)
Financing activities:
Proceeds from the issuance of long-term debt	0.0
Extinguishment of long-term debt	0.0	0.0	0.0
Repayments under credit facility	(1.0)	(1.0)	(1.0)
Debt issuance costs	0.0
Proceeds from the issuance of common stock	0.0	0.0
Proceeds from exercise of restricted stock units, employee stock options, and employee stock purchase plan	0.0	0.0	0.0
Financing from affiliated companies	0.0	0.0	0.0
Other, net			0.0
Net cash provided by (used in) financing activities from continuing operations	(1.0)	(1.0)	(1.0)
Net cash flows of continuing operations	4.9	(5.3)	1.3
Net operating cash flows of discontinued operations		0.0	(0.3)
Net investing cash flows from discontinued operations	0.0	0.0	(0.3)
Effect of exchange rate changes on cash and cash equivalents	0.5	(0.3)	(0.2)
Net increase (decrease) in cash and cash equivalents	$ 5.4	$ (5.6)	$ 0.5